Just remember that tattoos are *permanent*, they'll be there you're whole life. So don't get something that has meaning to you now but in 20 years from now will make you scratch your head and wonder what the hell it was supposed to be about. Also, as you age, the tattoo will deform. It will stretch, lose it's color and shape, and turn into a really ugly "thing" on your (insert body part) which looks really really disgusting.
One more note: If you plan to get a job in the professional world where you would be dealing with other people, make sure the tattoo is somewhere inconspicious that can easily be covered up (e.g. Upper arm, back, etc) Don't get them on the back of your neck or you'll be forced to wear a turtle neck every day at work. Don't get one on your calf unless you don't plan to wear shorts to work; don't get it on your lower arm unless you want to wear long sleeves every day, and don't get it on your hands unless you're okay with gloves *all* the time. Most companies, government agencies, and groups will not allow you to show your tattoo in public so they'll either not accept you, or make you wear things that cover up (long sleeve shirts, pants, turtle necks, gloves, etc...).
Alright, I've given my word of warning, so that in mind, have fun. I've found many tattoos to be cool and/or attractive - just do yourself a favor and don't get more than one, keep it relatively small; and make sure it has meaning that will last (don't put the name of your girlfriend on your forearm b/c you might break up with her and then start wondering how you could be such a complete idiot).